I'm booting BT 4 pre-final using a live CD. Could somebody explain the difference between the various boot options to me (frame buffer, persistent live CD, etc.)?

Regardless of which boot option one chooses, unlike BT 3 which booted straight onto the desktop for me, one has to always type 'startx' with BT 4 to get onto the desktop, correct? Is there a particular reason for that? After entering 'startx' I always get the error:

X: warning; process set to priority -1 instead of request priority 0
It boots onto the desktop just fine after showing that msg, but I was just wondering what that is all about and whether I am doing something wrong. Any ideas?

Thx

P.S.: My system is a Dell Inspiron 1520 laptop.